Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Industry Segment Information (Schedule Of Segment Reporting Information, By Segment) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Aug. 31, 2014	May 31, 2014	Feb. 28, 2014	Nov. 30, 2013	Aug. 31, 2013	May 31, 2013	Feb. 28, 2013	Nov. 30, 2012	Aug. 31, 2014	Aug. 31, 2013	Aug. 31, 2012
Segment Reporting Information [Line Items]
Total operating revenues	$ 147,522	$ 169,936	$ 152,804	$ 147,671	$ 148,397	$ 219,542	$ 175,539	$ 147,370	$ 617,933	$ 690,848	$ 551,255
Operating Income (Loss)									78,358	107,061	65,510
Unallocated general and administrative expenses									(43,228)	(43,441)	(45,423)
Interest and other income (expense), net									297	246	(402)
Total	16,549	25,500	20,789	15,817	15,686	39,750	29,488	22,383	78,655	107,307	65,108
Capital Expenditures									17,715	11,136	9,890
Depreciation and amortization									14,793	12,600	12,468
Assets	526,551				512,296				526,551	512,296	415,531
Irrigation [Member]
Segment Reporting Information [Line Items]
Total operating revenues									539,943	625,996	475,299
Capital Expenditures									15,534	10,687	7,942
Depreciation and amortization									9,494	7,147	6,959
Assets	407,447				391,527				407,447	391,527	303,741
Infrastructure [Member]
Segment Reporting Information [Line Items]
Total operating revenues									77,990	64,852	75,956
Capital Expenditures									2,181	449	1,948
Depreciation and amortization									5,299	5,453	5,509
Assets	119,104				120,769				119,104	120,769	111,790
Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating Income (Loss)									95,208	124,584	80,248
Operating Segments [Member] \| Irrigation [Member]
Segment Reporting Information [Line Items]
Operating Income (Loss)									91,697	125,395	80,259
Operating Segments [Member] \| Infrastructure [Member]
Segment Reporting Information [Line Items]
Operating Income (Loss)									3,511	(811)	(11)
Segment Reconciling Items [Member]
Segment Reporting Information [Line Items]
Unallocated general and administrative expenses									$ (16,850)	$ (17,523)	$ (14,738)